Water-resistant surface coating formulations and paper coated therewith

ABSTRACT

The present invention provides a water-resistant surface coating formulation comprising a reaction product obtained by subjecting an acrylamide polymer to a crosslinking reaction with 0.1 to 20 parts by mole, per 100 parts by mole of amido groups in the acrylamide polymer, of a glyoxalmonoureine; a method for improving the water resistance of paper by using the formulation; and coated paper so obtained. As a result of improved water resistance of the coating formulation, this invention makes it possible to conduct coating work stably.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a water-resistant surface coating formulationand also to paper coated therewith. More specifically, the presentinvention is concerned with a water-resistant surface coatingformulation containing a reaction product of an acrylamide polymer and aglyoxalmonoureine, a method for improving the water resistance of paperby using the coating formulation, and coated paper so obtained.

2. Description of the Related Art

There is an outstanding desire for improvements in the water resistanceof a surface coating formulation for paper, particularly for newsprintpaper and printing paper, because they are printed by offset printingwhich requires dampening water.

Various surface coating resins have heretofore been employed to reduceseparation of dust and/or filler from paper and/or to improve thesurface strength and printing applicability of paper. Preferredconventional examples of such coating resins include starch, oxidizedstarch and modified products thereof as natural products,carboxymethylcellulose and hydroxymethylcellulose as semisyntheticproducts, and polyvinyl alcohol, polyacrylamide and derivatives thereofas synthetic products. Furthermore, many resins such as urea resins,melamine resins, water-soluble epoxy resins, styrene-maleic acidcopolymers, polyvinyl acetate, vinyl acetate-maleic acid copolymers,latex resins and emulsion resins are used according to the applicationpurpose. They are used either singly or in combination. Among thesesurface coating resins, starch, polyvinyl-base and polyacrylamide-baseresins are employed preferably.

Although the above exemplified surface coating resins are significantlyeffective for obtaining paper having improved surface quality, theycause a variety of problems in relation to dampening water used at thetime of offset printing. Examples of the problem include frequent paperbreak which occurs because a surface coating resin dissolved bydampening water sticks on rollers and paper winds itself around theserollers; an adverse effect on the control of release of paper dust; andirregular coating and deteriorated printing applicability attributableto localized dissolution of a surface coating resin.

To cope with these problems, it is the general approach to improve thewater resistance of a coating resin. For starch or polyvinyl alcoholresins, it is the common practice to improve the water resistance byincorporating an epoxy resin or melamine resin. The starch resin havingimproved water resistance, however, requires a cumbersome dissolutionstep, and also involves other problems such as proneness to mildew andshort service life after dissolution. The polyvinyl alcohol resins arealso accompanied with problems such as irksome dissolution andtroublesome post-dissolution foaming.

Polyacrylamide resins are also used after being mixed or being partiallyreacted with a urea resin, melamine resin, epoxy resin, zirconium salt,glyoxal, ketone resin, wax emulsion and/or various sizing agents.Japanese Patent Publication Nos. 13686/1965 and 26670/1969 (USP 3853816et al.), for example, disclose a technique to react acrylamide withglyoxal, thereby improving the water resistance of the polyacrylamideresin. Japanese Patent Laid-Open No. 38705/1978 (USP 4122071, USP4170672) and Japanese Patent Publication No. 18713/1981 disclose atechnique to improve the water resistance of a polyacrylamide resin byusing a glycidyl-containing monomer. When glyoxal or theglycidyl-containing monomer is added in an amount sufficient to improvethe water resistance in the above technique, however, the coating resinso obtained is not stable in quality, for example, severe coloringoccurs or its service life is too short.

Modification of coating resins with a chemical substance is also underinvestigation. Use of a formaldehyde-containing composition as amodifier should however be avoided in view of the troublesome odor offormaldehyde. From the viewpoint of environmental protection, it shouldalso be avoided to use as a modier a chlorine compound which is a causefor dioxin contamination. Regarding paper quality, there is a demand forpaper having high performance sufficient to meet diversified requests,for example, having superior water resistance without deterioration insurface strength and printing applicability.

It is the present situation that no surface coating resin having bothlong service life and superior water resistance has been developed yet.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the present invention is to provide a surface coatingformulation having improved water resistance and also paper coated withthe formulation. Another object of the invention is to provide a surfacecoating formulation which has long service life and stable quality andpermits stable coating work. A further object of the invention is toprovide a surface coating formulation free of problems in pollution andthe like.

With the forgoing problems in view, the present inventors have conductedextensive research and, by partially crosslinking amido groups in ahydrophilic acrylamide resin to make it hydrophobic, hence completed thepresent invention.

The present invention therefore provides a water resistant surfacecoating formulation comprising a reaction product obtained by reactingan acrylamide polymer, which is a polymer or copolymer of an acrylamiderepresented by the following formula (1): ##STR1##

wherein X represents H or CH₃ and Y represents H or CH₂ OH, with 0.1 to20 mole parts, per 100 parts by mole of amido groups in the acrylamidepolymer, of a glyoxalmonoureine represented by the following formula(2): ##STR2##

wherein Q and R independently represent H, CH₃ or CH₂ OH.

DETAILED DESCRIPTION OF THE INVENTION

Examples of the acrylamide polymer usable in the present inventioninclude polymers and copolymers of acrylamides and copolymers of anacrylamide with at least one of (meth)acrylic acid, acrylonitrile anditaconic acid. Illustrative of the acrylamides include acrylamide,methacrylamide and N-substituted acrylamides such asN-methylolacrylamide, diacetone acrylamide, N,N-dimethylacrylamide,N,N-dimethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide,N,N-diethylacrylamide, N-propylacrylamide,2-acrylamido-2-methylpropanesulfonic acid,2-acrylamido-2-phenylpropanesulfonic acid, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropyl methacrylamide,N,N-dipropylacrylamide, N-butylacrylamide, N-hexylacrylamide,N-hexylmethacrylamide, N-octylacrylamide, N-octylmethacrylamide,N-dodecylacrylamide and N-dodecylmethacrylamide.

The comonomer component, such as (meth)acrylic acid, acrylonitrileand/or itaconic acid, of each acrylamide polymer may be used in anamount of 0 to 40 parts by mole relative to 100 to 60 parts by mole ofthe acrylamide, preferably 3 to 30 parts by mole relative to 97 to 70parts by mole of the compound. If the amount of the comonomer componentis greater than 40 parts by mole, the resulting surface coatingformulation is deteriorated in film forming property, surface strengthunder dry or wet conditions, controlling effects of paper dust or thelike. Amounts outside the above range are therefore not preferred. Asthe comonomer component, (meth)acrylic acid, acrylonitrile and itaconicacid may be used either singly or in any desired combinations.

In addition, the following substances can be added within a range of 0to 5 mole %. Examples include ethylenically-unsaturated carboxylic acidssuch as maleic acid, fumaric acid and crotonic acid; aromatic vinylcompounds such as styrene, α-methylstyrene, vinyltoluene anddivinylbenzene; alkyl methacrylates such as ethyl acrylate, butylacrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethylmethacrylate, butyl methacrylate and 2-ethylhexyl methacrylate;hydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate andhydroxyethyl methacrylate; vinyl pyrrolidone; glycidyl acrylate;glycidyl methacrylate; vinyl acetate; vinyl chloride; vinylidenechloride; methacrylonitrile and methylenebisacrylamide.

Acrylamide polymers can be produced by known radical polymerization.Although no particular limitation is imposed on a polymerizationcatalyst, persulfates such as potassium persulfate, sodium persulfateand ammonium persulfate-conventional water-soluble radical generators;peroxides such as hydrogen peroxide and benzoyl peroxide; and redoxcatalysts making use of the above peroxides in combination with reducingagents such as acidic sodium sulfite and sodium thiosulfate can beemployed. These redox catalysts are preferred because they permitpolymerization at low temperatures. No limitation is imposed on thepolymerization temperature. It it however desirable to initiatepolymerization at 20 to 40° C. in view of the polymerization heat of(meth)acrylamide.

A description will next be made of the reaction between an acrylamidepolymer and a glyoxalmonoureine.

The glyoxalmonoureine of the formula (2) is employed to efficientlycrosslink amido groups in the acrylamide polymer so that the polymer ismade hydrophobic. Examples of the glyoxalmonoureine represented by theformula (2) include glyoxalmonoureine, monomethylol glyoxalmonoureine,dimethylol glyoxalmonoureine, monomethyl glyoxalmonoureine, dimethylglyoxalmonoureine and monomethylmonomethylol glyoxalmonoureine. When theglyoxalmonoureine is used in an amount of 0.1 to 20 parts by mole,preferably 0.5 to 15 parts by mole, per 100 parts by mole of the amidogroups in the acrylamide polymer, a product having a suitable degree ofwater resistance can be obtained. Amounts smaller than 0.1 part by molecannot bring about any significant improvement in water resistance.Amounts greater than 20 parts by mole, on the other hand, result in anexcessive improvement in water resistance thereby making it difficult torecycle brokes and waste paper. Amounts outside the above range aretherefore not preferred.

The reaction between the acrylamide polymer and the glyoxalmonoureine isgenerally conducted in the form of an aqueous solution. As reactionconditions, they are usually reacted at 50°-80° C. for about 1-3 hours.

By forming cross-linkage between the individual molecules of theacrylamide polymer as described above, it is possible to obtain a resinhaving resistance to dampening water at the time of offset printing orthe like.

The reaction product so obtained from the acrylamide polymer and theglyoxalmonoureine has ordinarily a concentration of 5 to 25 wt. % and asolution viscosity of 500 to 15,000 cps as measured at 25° C., althoughthey vary depending on the molecular weight of the reaction product.

The surface coating formulation according to the present invention mayfurther contain a sizing agent, a water repellent and/or a waterproofingagent, such as a wax, an alkenyl succinate, rosin and/or an alkylketendimer, which impart water repellent property. Metal salts such aszirconium ammonium carbonate, zirconyl acetate, zirconyl nitrate, basiczirconium carbonate, zirconyl phosphate and zirconyl hydroxide, variousresins, emulsions and latexes can also be used in combination.

Conventional processing methods can be used to apply the thus-preparedsurface coating formulation to paper. For example, paper can be coatedby a coater such as a gate roll coater, calender roll coater, rollcoater or air knife coater. Alternatively, paper can be treated by amethod such as impregnation or spraying.

The water-resistant resin according to the present invention is used ina manner known per se in the art. To adjust the coat weight according tothe degree of waterproofness required, the surface coating formulationmay be used neat or after diluted with water or the like as needed.

The water-resistant coating formulation of the present invention appliedto paper exhibits excellent initial water resistance against dampeningwater at the time of offset printing without impairing printingapplicability or causing the problem of paper dust. It can, therefore,be provided as a useful resin for which there is an outstanding need.

The present invention will hereinafter be described in further detail byExamples and Comparative Examples. It is to be noted that these examplesare merely illustrative and are not intended to limit the presentinvention thereto.

Incidentally, all designations of "%" and "part" or "parts" mean wt. %and part or parts by weight unless otherwise specifically designated.

Example 1

In a 1-l separable flask, 485 g of water and 450.7 g of a 40% aqueoussolution of acrylamide were charged and were stirred and mixed at roomtemperature. To the resulting mixture, 1/10 N hydrochloric acid wasadded to adjust its pH to 6.0. The internal temperature was then raisedto 35° C., followed by the addition of 10 ml of a 10% aqueous solutionof potassium persulfate and, 5 minutes later, 5 ml of a 10% aqueoussolution of acidic sodium sulfite. The reaction then proceeded rapidlywith exotherm. About 10 minutes later, the internal temperature arose to91° C. and the reaction mixture turned into a viscous aqueous solution.The reaction was continued for further one hour, whereby an aqueouspolymer solution having a solid content of 18% and a viscosity of 50poises was obtained. The aqueous polymer solution was then added with49.5 g of a 40% aqueous solution of dimethyl glyoxalmonoureine whilebeing kept at 65°-70° C. They were reacted at the same temperature for 3hours, whereby Reaction Product 1 having a solid content of 20% and aviscosity of 57 poises at 25° C. was obtained.

The molar ratio of the acrylamide to the dimethyl glyoxalmonoureine inReaction Product 1 was 95:5.

Example 2

In a similar manner to Example 1 except that 485 g of water and 407 g ofa 40% aqueous solution of acrylamide were charged and 93 g of a 40%aqueous solution of dimethyl glyoxalmonoureine were added, ReactionProduct 2 having a solid content of 20% and a viscosity of 49 poises at25° C. was obtained.

The molar ratio of the acrylamide to the dimethyl glyoxalmonoureine inReaction Product 2 was 90:10.

Example 3

In a similar manner to Example 1 except that 85 g of water and 441.8 gof a 40% aqueous solution of acrylamide were charged and 61.8 g of a 38%aqueous solution of dimethylol glyoxalmonoureine were added, ReactionProduct 3 having a solid content of 20% and a viscosity of 53 poises at25° C. was obtained.

The molar ratio of the acrylamide to the dimethylol glyoxalmonoureine inReaction Product 3 was 95:5.

Example 4

In a similar manner to Example 1 except that 485 g of water and 391.0 gof a 40% aqueous solution of acrylamide were charged and 113.9 g of a38% aqueous solution of dimethylol glyoxalmonoureine were added,Reaction Product 4 having a solid content of 20% and a viscosity of 59poises at 25° C. was obtained.

The molar ratio of the acrylamide to the dimethylol glyoxalmonoureine inReaction Product 4 was 90:10.

Example 5

In a similar manner to Example 1 except that 498 g of water, 384.3 g ofa 40% aqueous solution of acrylamide, 6.24 g of an 80% aqueous solutionof acrylic acid and 3.68 g of acrylonitrile were charged and 13.5 ml ofa 10% aqueous solution of potassium persulfate, 6.7 ml of a 10% aqueoussolution of acidic sodium sulfite and 94 g of a 40% aqueous solution ofdimethyl glyoxalmonoureine were added, Reaction Product 5 having a solidcontent of 20% and a viscosity of 55 poises at 25° C. was obtained.

The molar ratio (%) of the acrylamide, the acrylic acid and theacrylonitrile in Reaction Product 5 was 94:3:3, while the molar ratio ofthe whole vinyl monomers to the dimethyl glyoxalmonoureine was 90:10.

Example 6

In a similar manner to Example 1 except that 504 g of water, 345 g of a40% aqueous solution of acrylamide, 6.1 g of an 80% aqueous solution ofacrylic acid and 8.79 g of itaconic acid were charged and 13.5 ml of a10% aqueous solution of potassium persulfate, 6.7 ml of a 10% aqueoussolution of acidic sodium sulfite and 91 g of a 40% aqueous solution ofdimethyl glyoxalmonoureine were added, Reaction Product 6 having a solidcontent of 20% and a viscosity of 47 poises at 25° C. was obtained.

The molar ratio of the acrylamide, the acrylic acid and the itaconicacid in Reaction Product 6 was 4:3:3, while the molar ratio of the wholevinyl monomers to the dimethyl glyoxalmonoureine was 90:10.

Example 7

In a similar manner to Example 1 except that 497 g of water, 360.5 g ofa 40% aqueous solution of acrylamide, 5.83 g of an 80% aqueous solutionof acrylic acid and 8.43 g of itaconic acid were charged and 13.5 ml ofa 10% aqueous solution of potassium persulfate, 6.7 ml of a 10% aqueoussolution of acidic sodium sulfite and 112.5 g of a 38% dimethylolglyoxalmonoureine were added, Reaction Product 7 having a solid contentof 20% and a viscosity of 46 poises at 25° C. was obtained.

The molar ratio of the acrylamide, the acrylic acid and the itaconicacid in Reaction Product 7 was 94:3:3, while the molar ratio of thewhole vinyl monomers to the dimethylol glyoxalmonoureine was 90:10.

Comparative Example 1

In a 1-l separable flask, 485 g of water and 500 g of a 40% aqueoussolution of acrylamide were charged and were stirred and mixed at roomtemperature. To the resulting mixture, 1/10 N hydrochloric acid wasadded to adjust its pH to 6.0. As soon as the internal temperaturereached 35° C., 10 ml of a 10% aqueous solution of potassium persulfateand, 5 minutes later, 5 ml of a 10% aqueous solution of acidic sodiumsulfite were added to the reaction mixture. The reaction proceededrapidly with exotherm. About 10 minutes later, the internal temperaturearose to 90° C., forming a viscous aqueous solution. After the reactionwas continued for further one hour, the reaction mixture was cooled downto 80° C. and then neutralized with 1/10 N caustic soda, whereby anaqueous acrylamide polymer solution having a solid content of 20% and aviscosity of 45 poises at 25° C. was obtained.

Comparative Example 2

The reaction was conducted in a similar manner to Example 1 except that485 g of water and 266.9 g of acrylamide were charged and 233 g of a 40%aqueous solution of dimethyl glyoxalmonoureine were added. About onehour after the addition of dimethyl glyoxalmonoureine, gelation occurredand the resulting gel started winding itself around a stirring rod, sothat the reaction was terminated. The molar ratio of the acrylamide tothe dimethyl glyoxalmonoureine in the mixture was 70:30.

Comparative Example 3

As prior art, a 10% aqueous solution of commercially-available PVA wasemployed as Comparative Example 3.

According to an evaluation testing method which will be described below,the compositions obtained in Examples 1-7, the aqueous acrylamidepolymer solution obtained in Comparative Example 1 and the 10% aqueousPVA solution in Comparative Example 3 were compared. Testing methods forthe evaluation of performance as paper surface coating formulations:

1. Test for judgment of initial water resistance

In this test, measurement is made according to the procedures describedbelow under (1) to (7). Test results indicate the resistance of coatedsamples to water. Low peeling strength suggests that the coated sampleis rather free from break, that is, the phenomenon which occurs when thesurface coating resin dissolved by dampening water sticks on rollersupon printing and paper winds itself around the rollers.

(1) Provide a blade coater for testing. Using the coater, coat inadvance water to newsprint base paper having a basis weight of 48 g/m²and calculate the coating build-up of water per m².

(2) Based on the coating build-up of water so calculated, adjust theconcentrations of the compositions in Examples 1 to 7 and the aqueousresin solutions in Comparative Examples 1 and 3 to 4-8% to give resincoat weights of 0.3 and 0.6 g/m²

(3) Weigh each base paper precisely to the unit of 1 mg and provide adrum drier preset at 105° C. in advance.

(4) Set the precisely-weighed base paper on the blade coater and applyeach aqueous solution to the paper while operating the coater. Measurethe coat weight, dry the paper in a drum drier and then subject thedried paper to seasoning at constant temperature and humidity of 20° C.and 65% for 24 hours. Provide two sheets of coated paper in the abovemanner.

(5) Warm up a laboratory mini-calender to 50° C. in advance. Fill ashallow vat with water. Provide a No.2 square filter paper whose widthis a little greater than the coated paper.

(6) Place one of the coated papers on water so that its coated surfaceis brought into contact with water. Bring the paper into a contiguousrelation with the other one, i.e., the dry paper so that their coatedsurfaces are bonded together. Place the bonded sample so obtainedbetween two sheets of the filter paper and pass them through a calender.Repeat this operation three times with replacement of the filter paperafter each operation. Subject the bonded sample to seasoning overnightin an air-conditioned chamber.

(7) Cut the bonded sample so obtained into widths of 3 cm. Peel off thesample at a part thereof and then peel it off from the peeled part byusing a Tensilon tensile tester to measure its peeling strength.

2. Water solubility test

The compositions obtained in Examples 1 to 7 and aqueous polymersolutions obtained in Comparative Examples 1 and 3 were weighed, about10 g each, in aluminum cups, respectively. They were diluted with asuitable amount of water and then dried for 24 hours in a roomtemperature vacuum drier, whereby films were obtained. About 0.5 g ofeach film was weighed precisely, placed in a 100-ml Erlenmeyer flask andadded with 50 ml of water, followed by stirring on a shaker for 5minutes. Any undissolved part of the film was thereafter taken out ofthe flask and dried at 105° C. for 2 hours. The weight of the film afterdried was measured and the amount of the film dissolved in water wasdetermined.

Results of the water solubility test are shown in Table-1.

                  TABLE 1                                                         ______________________________________                                                    Resin coat weight                                                                        Weight                                                             (g) and    dissolved                                                          peeling strength*                                                                        in water                                               Test No.    A           B      (%)                                            ______________________________________                                        Example 1   12          21     4                                              Example 2   10          18     2                                              Example 3   11          23     3                                              Example 4    9          17     3                                              Example 5   10          20     3                                              Example 6   13          25     2                                              Example 7   13          21     3                                              Comp. Ex. 1 68          103    13                                             Comp. Ex. 3 203         298    3                                              ______________________________________                                         *A indicates peeling strength at a coat weight of 0.3 g/m.sup.2 and B at      0.6 g/m.sup.2.                                                           

As can be seen from Table 1, the bonded sample coated with any one ofthe surface coating formulations according to the present invention hadrelatively low peeling strength and the film formed from any one of thesurface coating formulations according to this invention had a smallweight dissolved in water, thereby demonstrating effects ofcrosslinking. This indicates that the reaction product in each surfacecoating composition according to this invention had low solubility inwater and has resistance to water at the time of offset printing. InComparative Example 1, on the other hand, the bonded sample had highpeeling strength and the film had a large weight dissolved in water. InComparative Example 3, the weight dissolved in water is small but thepeeling strength is extraordinarily high, thereby indicating theexistence of a problem.

We claim:
 1. A water-resistant surface coating formulation comprising areaction product obtained by reacting an acrylamide polymer of at leastone acrylamide monomer represented by the following formula ##STR3##wherein X represents H or CH₃ and Y represents H or CH₂ OH, and,optionally, at least one comonomer selected from the group consisting ofacrylic acid, methacrylic acid, acrylonitrile and itaconic acid, with0.1 to 20 parts by mole, per 100 parts by mole of amido groups in theacrylamide polymer, of a glyoxalmonoureine represented by the followingformula (2): ##STR4## wherein Q and R independently represent H, CH₃ orCH₂ OH; wherein the acrylamide polymer is produced from 100 to 60 partsby mole of the at least one acrylamide represented by the formula (1)and 0 to 40 parts by parts by mole of at least one comonomer selectedfrom the group consisting of acrylic acid, methacrylic acid,acrylonitrile and itaconic acid.
 2. A water-resistant surface coatingformulation according to claim 1, wherein the acrylamide polymer ispolyacrylamide.
 3. A water-resistant surface coating formulationaccording to claim 1, wherein the glyoxalmonoureine represented by theformula (2) is selected from the group consisting of glyoxalmonoureine,monomethylol glyoxalmonoureine, dimethylol glyoxalmonoureine, monomethylglyoxalmonoureine, dimethyl glyoxalmonoureine and monomethylmonomethylolglyoxalmonoureine.
 4. A water-resistant surface coating formulationaccording to claim 1, wherein the glyoxalmonoureine has been reacted inan amount of 0.5-15 parts by mole per 100 parts by mole of amido groupsin the acrylamide polymer.
 5. A water-resistant surface coatingformulation according to claim 1, wherein the acrylamide polymer hasbeen obtained by polymerizing 97 to 70 parts by mole of the acrylamiderepresented by formula (1) and 3 to 30 parts by mole of the comonomercomponent.
 6. A water-resistant surface coating formulation according toclaim 1 wherein the acrylamide polymer is produced from the at least oneacrylamide monomer and the at least one comonomer selected from thegroup consisting of acrylic acid, methacrylic acid, acrylonitrile andiraconic acid.
 7. A water-resistant surface coating formulationaccording to claim 1 wherein the acrylamide polymer is produced from theat least one acrylamide monomer and in the absence of the at least onecomonomer.
 8. A water-resistant surface coating formulation according toclaim 1 wherein the at least one acrylamide is selected from the groupconsisting of acrylamide, methacrylamide, N-methylolacrylamide,diacetone acrylamide, N,N-dimethylacrylamide,N,N-dimethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide,N,N-diethylacrylamide, N-propylacrylamide,2-acrylamido-2-methylpropanesulfonic acid,2-acrylamido-2-phenyl-propanesulfonic acid, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropyl methacrylamide,N,N-dipropylacrylamide, N-butylacrylamide, N-hexylacrylamide,N-hexylmethacrylamide, N-octylacrylamide, N-octylmethacrylamide,N-dodecylacrylamide and N-dodecylmethacrylamide.
 9. A water-resistantcoating formulation according to claim 1 wherein the acrylamide polymeris further produced from at least one substance present in an amount of0-5 mol % and which is selected from the group consisting ofethylenically-unsaturated carboxylic acids, aromatic vinyl compounds,alkyl methacrylates, hydroxyalkyl (meth)acrylates, vinyl pyrrolidine,glycidyl acrylate, glycidyl methacrylate, vinyl acetate, vinyl chloride,vinylidene chloride, methacrylonitrile and methylenebisacrylamide.